68 



SCIENCE- GOSSIP. 



arborea. There are nearly 200 recognised species 

 throughout the -world, their headquarters being in 

 the tropical forests of South and Central America. 

 They extend, however, throughout the temperate 

 and tropical regions of both North and South 

 America, Europe, Asia, and the whole of Aus- 

 tralia, but have not occurred in Africa, except in 

 that portion adjacent to Europe. Some of these 

 pretty little amphibia have the power of changing 

 colour, apparently for protective purposes. Bieder- 

 mann has found that under a low power of a 

 microscope and direct light is seen " a mosaic of 

 green polygonal areas, separated by dark lines and 

 interrupted by openings of the skin-glands." 

 These cells have a basal half which is granular 

 and colourless, whilst the upper half is of a 

 different character, containing colour according to 



species. By contraction or expansion of these 

 cells the effects of colour-change are attained. 

 Low temperature causes expansion, and high 

 temperature contraction. There appears, however, 

 to be some sense governing the changes of colour 

 in tree-frogs, as they will turn from a dull brown 

 to bright green if confined with leaves in a dark 

 vessel where the colour of the leaves is not 

 visible. The sense of touch with the leaves- 

 appears to react upon the colour cells. Probably 

 not voluntary, but reflex action is the cause of 

 colour-change. Still, we cannot imagine that the 

 whole effect is produced without some intention on 

 the part of the tree-toad. The homing instinct, or 

 habit, of most reptiles is well developed, but in 

 none more than iD " tree-frogs," as exemplified by 

 Mr. Jeune in the instance above quoted. — Ed. S.-G.] 



BRITISH FRESHWATER MITES. 



By Charles D. Soar, F.R.M.S. 

 WITH THREE NEW SPECIES. 



(Continued from Vol. VII., p. 204.) 



GENLS EYLAIS (continued). 



TN last December's number of Science-Gossip I 

 -^ recorded two species of the genus Eylais — 

 E. discreta Koenike, and E. soari Piersig. I also 

 mentioned that I had others, but had not been 

 able to identify them. I wrote to Dr. Piersig 

 about these, and he advised me to name those I 

 could not identify, or fit in with his key, and I 

 have now done so. I have the pleasure to place 

 before your readers six more species, three being 

 new and three already described by other writers. 

 This brings the number of English species in the 

 genus up to eight. I have before mentioned that 

 the great point of identification in Eylais is the 

 eye-plates. The whole of Piersig's key for twenty- 

 three species is founded on this character ex- 

 cepting two, which show a great difference in the 

 palpi. 



3. Eylais dividuus nov. sp. 



Body. — About 3 - 4 mm. in length, and of the 



Fig. 1. Eylais dividuus. Eye-plate. 



usual form. Dark-red in colour. Its general 

 description is about the same as for other members 



of this genus, its great difference from those pre- 

 viously mentioned being in the eye-plates. The 

 nearest species I have been able to find to this one 

 is Eylais emarginator Piersig, both being about the 

 same size. In Piersig's E. emarginator the hinder 

 bow line is bisected by a small projecting point, 

 which extends over the line. The disc, which is in 

 the centre of the eye-bridge, is heart-shaped, and 

 it is the lower point which projects over the line. 

 There is also a small spot on each side of the disc. 

 In E. dividuus the central disc is quite elliptical, 

 without spots on either side, and it is divided 

 down the centre to nearly close to the bow line. 

 The extreme width across the eye-plates is about 

 - 4 mm. 



Locality. — East London Waterworks, October 

 6th, 1900. Only two specimens taken. 



4. Eylais georgei nov. sp. 



Length about 2 - 40 mm. 



This mite is quite different in the eye-plates to- 

 any description I have yet seen. The nearest is 

 E. megalostoma Koenike, 1897, but it differs very 

 much from that species. In E. megalostoma there 

 are two discs projecting forward beyond the eye- 

 plates at each end of the bridge, and two others in 

 a similar position on the hinder curve. In E. 

 georgei there are two discs, only well in the band 

 which forms the bridge (see figs. 2, 3, 4). Width 

 across the eyes about - 45 mm. I have drawn 

 three figures to this species to show how individual 

 specimens vary ; although all are of the same size,, 

 not any are alike. 



